1. Field of the Invention
This invention relates to integrated circuit interconnections and the method of forming them. More particularly, it relates to a bondhead assembly with a substantially linear stroke.
2. Description of the Prior Art
Conventional bonding apparatus for forming microelectronic interconnecting bonds, have utilized an arcing motion for many years. Conventional bondheads are typically moved by some kind of linkage such as the four-bar linkage of FIG. 1. The mechanical linkage attached to the conventional bondhead assembly results in a lack of precision in positioning the bondhead assembly as well as a lack of precision in the bonding stroke itself. The arcing motion also causes limited control of the bonding force. Additionally, since the capillary or other bonding tool is not approaching the bond site in a vertical orientation, there is a lack of physical optimization of the bonding parameters. In particular, the lack of perpendicularity between bonding tool and bonding site diminishes the transmission of ultrasonic energy.
One problem with conventional bonders is the lack of access to packages which are geometrically or physically difficult to reach (e.g. "deep access" packages). One example of such a package is a pin grid array (PGA) presenting multiple planes of access for bonding purposes or for access purposes, and thus portions of the bonding apparatus may be obstructed by the geometry of the package. In addition, certain packages may have different levels at which bonding must be performed, thus creating inherent precision problems with the above-discussed technology. That is to say, if the bondhead is aligned to be substantially perpendicular for bonding at one level (e.g. leadframe level) it will be skewed at another level (e.g. die level).
Another problem attendant with the conventional technology is that the wire being fed through the capillary has a hazardous route as it is fed into the bondhead assembly. In other words, any number of physical obstructions, operator accidents or inadvertent contact with equipment in the area can lead to nicks and/or bends in the wire. These kinds of unintentional impacts on the wire can often lead to undesirable, permanent deformation thereof.
What is needed is a bonding apparatus which provides flexible access (e.g. for deep access packages or multilevel packages) with the capability for more precision in positioning and the bonding stroke of the bondhead assembly. In addition, it would be highly desirable to have a bonding apparatus which better protected the bonding wire.